OBJECTIVE: We reviewed the features of nystagmus in 24 patients with horizontal canal benign positional vertigo (BPV). Patients were treated with canalith repositioning maneuvers. Our goal was to develop a framework for distinguishing horizontal from posterior canal BPV and to further develop a mechanistic model explaining the horizontal canal variant of BPV. STUDY DESIGN: The study design was a retrospective case review with prospective treatment outcome and follow-up. SETTING: The study was performed at a secondary and tertiary referral center for vertigo and dizziness. PATIENTS: The diagnosis of horizontal canal BPV was based on: 1) recurrent brief episodes of positional vertigo; 2) paroxysmal bursts of horizontal positional nystagmus; and 3) lack of any other identifiable central nervous system disorder to explain the nystagmus. Patient average age was 62 years, and average duration of symptoms was 12 weeks. INTERVENTIONS: We documented patients' symptoms and the characteristics of nystagmus. We reviewed the effectiveness of several similar canalith repositioning treatments. MAIN OUTCOME MEASURE: We observed and recorded factors that distinguish horizontal from posterior canal BPV. We monitored the direction of nystagmus, the type of maneuver that evoked the nystagmus, and the response to canalith repositioning. RESULTS: Symptom description alone was not sufficient to distinguish among canal types of BPV. Horizontal geotropic direction-changing positional nystagmus was observed in 19 of 24 patients. The other patients had ageotropic nystagmus. Both types were distinct from the nystagmus of posterior canal BPV. Response to canalith repositioning was 75% at 1 week of follow-up. Conversion of BPV from one canal to another occurred in some patients, but each canal could be treated individually. CONCLUSIONS: Patients with positional vertigo should undergo Dix-Hallpike positioning and supine lateral head turns to each side. Paroxysmal positional horizontal nystagmus that changes direction with changes in head position strongly suggests the diagnosis. Canalith repositioning for posterior canal BPV may fail in horizontal BPV. A 360 degrees barbecue rotation toward the presumably healthy ear done two to four times or until nystagmus disappears may result in more rapid resolution of symptoms.
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